Peripheral shield for color television tube shadow masks



Oct. 10, 1967 PHAAS 3,346,753.

PERIPHERAL SHIELD FOR COLOR TELEVISION TUBE SHADOW MAsKs Filed May 2, 1966 INVENTOR. PAUL HAAs v ATTORNEY United States Patent .C

3,346,753 PERIPHERAL SHIELD FR COLOR TELEVISION TUBE SHADOW MASKS Paul Haas, Seneca Falls, N.Y., assignor to Sylvania Electric Products Inc., a corporation of Delaware Filed May 2, 1966, Ser. No. 546,645 5 Claims. (Cl. 313-92) This invention relates to image display devices and more particularly to color cathode ray tubes as employed in television apparatus.

In certain types of color cathode ray tubes, one or more electron beams are directed through an electron permeable member or foraminous shadow mask to impinge a spacedly related cathodoluminescent screen comprising electron responsive color phosphors disposed in discrete patterns of dots, bars, or stripes.

The foraminous mask is conventionally supported on a peripheral frame which is positioned within the tube panel portion on support means extending therefrom.

During the usual procedure utilized in forming the screen pattern on the Viewing panel of shadow mask tubes, it is necessary to remove and precisely reinsert the mask therein several times. Such movement of the mask is facilitated by having the mask supporting frame dimensioned smaller than the internal dimensions of the panel to effect a peripheral spacing therearound.

In tube operation, it has -been found that some of the over-scan electron beams strike portions of the interior wall of the funnel and/or panel in a manner that the reflected electrons are directed to pass through the aforementioned peripheral spacing and impinge phosphor areas of the screen not associated with intended beam irnpingement. The phosphors thus spuriously excited by the reflected electrons are predominately inthe peripheral regions of the screen and effect areas of olf-white haze which are deleterious to desired color purity of the screen display. To overcome this undesirable condition, thin metallic shields or iin-like projections are often oriented to cover the spacing between the mask frame and the panel sidewall when the mask has been finally positioned within the panel. Unfortunately, the temperatures encountered in tube processing sometimes cause these iins to slightly deform and provide inadequate electron shielding. At this stage of tube manufacturing there is no means for correcting defective shielding.

Accordingly, it is an object of the invention to reduce the aforementioned disadvantages and to provide a color cathode ray tube that presents a display of improved color purity.

Another object is to provide continuous and consistent peripheral shielding of the mask-panel spacing in a manner capable of economic fabrication.

A Afurther object is to provide adequate shielding even in those instances where the edge of the shield may be pulled away from the panel sidewall.

The foregoing objects are achieved in one aspect of the invention by the provision of a cathode ray tube having a metallic electron dispersion shield with a seating portion formed for attachment to the mask frame. A U-shaped channel integral to the seating portion is formed to extend peripherally around the shadow mask frame in a continuous manner to make a wedge-like concave lit between the frame and the panel sidewall and resiliently bridge the peripheral spacing therebetween. The channel portion has a proximal wall adjacent the mask frame extending to the concavity portion of the channel, and a substantially opposed distal wall, having a height greater than that of the proximal wall, formed to extend in a substantially upstanding manner from the concavity portion to a terminal leading edge to make contact with the panel sidewall.

37,346,753 Patented Oct. 10, 1967 ICC For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following specification and appended claims in connection with the accompanying drawings in which:

FIGURE l is a sectional view showing the positioned electron dispersion shield; and

FIGURE 2 is an enlarged sectional similar to FIGURE l illustrating a type of beam dispersion.

With reference to the drawings, partial structures of a shadow mask cathode ray tube 11 are shown. A funnel portion 12 has at least one electron source 13 positioned in the mask region thereof to project electron beams 15 through the foraminous shadow mask 17 to impinge the electron-responsive phosphors comprising the cathodoluminescent screen 19 disposed on the tube viewing panel 21. The shadow mask supporting frame 23 is positioned within the panel to be spaced from the sidewall 25 thereof. Over-scan beams or reflected electrons 15 from funnel impingement are directed toward the aforementioned spacing where they are desirably stopped by proper shielding.

The channelized electron dispersion shield 27 has a seating portion 29 oriented on the mask frame with a raised convexly rolled beading 31 peripherally therearound which makes integral transition to an adjacent U-shaped channel 33. This channel is formed to extend peripherally varound the frame in a substantially continuous manner and is of a width to make a wedge-like concave t between the frame and the panel sidewall to effectively bridge the spacing therebetween in a resilient manner. The shield is fabricated of thin metallic material such as aluminum and may bev of one-piece or multiple section overlapping construction. In greater detail, the channel 33 has a proximal wall 35 which extends from the periphery of the beading 31 of the seating portion to the concavity portion 37 of the channel. Substantially opposed to the proximal wall is a distal wall 39 which extends in a substantially upstanding manner from the concavity portion of the channel to a terminal leading edge 41 which substantially makes contact with the panel sidewall. It has been found that the aforementioned terminal edge 41 should preferably extend above the plane 32 of the apex of the beading 31 to enhance the desired contact.

The distal wall has a height X which is greater than height Y of the proximal wall. It has been discovered that the extra height of the distal wall is of at least twofold importance. It affords enhanced resilience to the channel, in conjunction with the opposite beading of material, when the wedge-like lit is consumated. This extra resilience has been found to be beneficial in maintaining the desired bridging of the spacing as the resilience tends to keep the spacing closed during tube processing.

These are instances when deadening of the shield material and the contraction upon cooling causes a slight retraction of the leading edge 41 of the distal wall from the panel sidewall 25. This results in a slit-like opening or canyon-effect into which reflected or discretely beamed electrons may enter. It has been found that this condition can be counteracted by orienting the distal Wall in angular relationship with the panel Isidewall in a manner to consummate an angle 0 of less than l5 degrees therewith. With reference to FIGURE 2, the over-scan or reflected electrons 15' enter the opening between the leading edge of the distal wall and the panel sidewall, but because of the length of the distal wall and its angular proximity with the panel sidewall, the spurious electrons are bounced back and forth and are thus harmlessly dispersed before they can reach the screen.

The shield seating portion 29 may be attached to the frame 23 by welding, bonding or by another means which has been found to be quite expedient. A plurality of compatible perforations 43 and 43' are concentrically formed in spaced relationship in the seating portion and frame respectively. Into these perforations, resilient means such as spring clips 45 are inserted to facilitate positive attachment of the shield to theframe. l

There is thus provided improved electron dispersion and shielding means to prevent over-scan and reected electrons from entering the spacing between the shadow mask frame and the panel sidewall. The channelized shaping provides shielding sidewalls that facilitate a resilient wedge-like fit into the spacing. The beading peripheral to the channel provides the extra material necessary for the resilient fit and additionally lends lateral strengthening to the shield structure. The length of the distal wall and its angular proximity to the panel sidewall act conjunctively to disperse electrons which may enter the spacing as a result of dimensional changes in the shield occurring from tube processing heat.

The attachment of the formed shield to the shadowmask frame may be repetitively accomplished in a consistent manner in keeping with desired economic fabrication techniques.

While there has been shown and described what is at present considered the preferred embodiments of the invention it will be obvious to those skilled in the art that various changes and modiiications may be made therein without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. In a color cathode ray tube having a funnel portion, a viewing panel integrally joined thereto with a substantially up'standing perimetrical sidewall portion, a multipattern cathodoluminescent screen disposed on the inner surfaces of said panel, a frame supported foraminous mask positioned within said panel on supoprt means extending therefrom to provide spaced relationship with said screen, anda source of electrons oriented to beam said electrons through said mask to discretely excite the electron responsive color phosphors in said screen, that improvement therein which comprises metallic means for shielding the peripheral portion of said screen from electrons peripherally reflected from the panel sidewall during tube operation in the form of:

a channelized electron dispersion shield having a seating portion formed for attachment to said frame with a substantially U-shaped channel portion integral thereto being formed to extend peripherally around said frame in a substantially continuous manner to provide a wedge-like concave iit between said frame and said panel sidewall and resiliently bridge the peripheral spacing therebetween, said channel portion having a proximal wall adjacent said frame extending from the periphery of said seating portion to the concavity portion of said channel and a substantially opposed distal wall extending a substantially upstanding manner from said concavity portion to a terminal leading edge to substantially make contact with said panel sidewall, said upstanding portion of said distal wall being oriented in angular relationship with said panel sidewall.

2. A cathode ray tube Ishielding means acocrding to 'claim 1` wherein said substantially upstanding portion of said distal wall is oriented in angular relationship with said panel sidewall to consummate an angle of less than 15 therewith.

3. A cathode rayk tube shielding means according to claim 1 wherein said distal wall has a height greater than that of said proximal wall.

4.'A cathode ray tube shielding means according to claim 1 wherein said seating portion has a raised convexly rolled peripheral beading from which said proximal sidewall integrally extends to provide lateral strengthening and resilience to the fitting of said channel portion between said frame and said panel sidewall, said leading edge of said distal wall being formed to extend above the plane of the apex of said beading.

5. A cathode ray tube according to claim 1 wherein said frame and said shield seating portion have a plurality of compatible concentric perforations formed therethrough and spaced therearound, and a pluraiity of resilient attachment means formed to t said perforations to provide attachment of said shield to said frame.

No references cited.

DAVID I. GALVIN, Primary Examiner. VINCENT LAFRANCHI, Assistant Examiner. 

1. IN A COLOR CATHODE RAY TUBE HAVING A FUNNEL PORTION, A VIEWING PANEL INTEGRALLY JOINED THERETO WITH A SUBSTAN TIALLY UPSTANDING PERIMETRICAL SIDEWALL PORTION, A MULTIPATTERN CATHODOLUMINESCENT SCREEN DISPOSED ON THE INNER SURFACES OF SAID PANEL, A FRAME SUPPORTED FORAMINOUS MASK POSITIONED WITHIN SAID PANEL ON SUPPORT MEANS EXTENDING THEREFORM TO PROVIDE SPACED RELATIONSHIP WITH SAID SCREEN, AND A SOURCE OF ELECTRONS ORIENTED TO BEAM SAID ELECTRONS THROUGH SAID MASK TO DISCRETELY EXCITE THE ELECTRON RESPONSIVE COLOR PHOSPHORS IN SAID SCREEN, THAT IMPROVEMENT THEREIN WHICH COMPRISED METALLIC MEANS FOR SHIELDING THE PERIPHERAL PORTION OF SAID SCREEN FORM ELECTRONS PERIPHERALLY REFLECTED FROM THE PANEL SIDEWALL DURING TUBE OPERATION IN THE FORM OF: 